Diseases are the result of abnormal up or down regulation of multiple proteins in the body affecting different physiological pathways. Unregulated angiogenesis, pathological conditions, and pathogen agents cause this abnormal regulation of proteins. The available drugs to treat many of these disease conditions target single proteins and only provide modest and transient clinical effects but do not cure the targeted diseases; hence there is a persisting need to develop multi-targeted therapeutics.
Angiogenesis, the growth of new blood vessels from existing vessels, is an integral component of many physiological and pathological conditions such as wound healing, inflammation, and tumor growth (Folkman, J. and Klagsbrun, M. (1987) Science, 235: 442-447). Under abnormal conditions, angiogenesis can either directly or indirectly cause a particular disease that may include cancer, metastasis, solid tumors, diabetes, inflammation, cardiovascular disease, rheumatoid arthritis, psoriasis, inflammatory diseases, and Alzheimer's and Parkinson's diseases, and related neurological disease conditions, brain disorders, neurodegenerative disorders, neuropsychiatric illnesses, bipolar disorder, and diseases caused by aging. Angiogenesis may also exacerbate an existing pathological condition leading to other diseases, including eye retinopathies such as wet age-related macular degeneration, choroidal neovascularization, diabetic retinopathy, diabetic macular edema, retinal vein occlusion and retinal angiomatus. These angiogenesis-dependent diseases are the result of new blood vessels growing excessively. In these conditions, new blood vessels feed diseased tissues and destroy normal tissues, and in the case of cancer, the new vessels allow tumor cells to grow and establish solid tumors or to escape into the circulation and lodge in other organs leading to tumor metastases.
Growth factors are capable of stimulating cellular growth, proliferation, and cellular differentiation and are involved in most cancers. They are important for regulating a variety of cellular processes and act as signaling molecules between cells (Welsh et al. Amer. J. Surg.194, 2007, S76-S83). Excessive angiogenesis occurs when diseased cells produce abnormal amounts of growth factors or pro-angiogenic factors, overwhelming the effects of natural angiogenesis inhibitors. Pro-angiogenic growth factors may include vascular endothelial growth factor (VEGF-A, B and C), fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF-a/b), epidermal growth factor (EGF), proepithelin (PEPI) or PC cell-derived growth factor (PCDGF) among many others (Marjon P L et al. Molecular Cancer 2004, 3:1-12; Kwabi-Addo B et al. Endocr Relat Cancer. 2004 11(4):709-24).
Cancer is caused by over-expression and up-regulation of growth factors implicated in many physiological pathways and endocrine functions. Abnormal cells divide without control, and migrate and spread to any tissue through the blood and lymph systems (Hanahan D, Weinberg R A. Cell. 2000, 100(1):57-70). The most common cancers include breast, colon, pancreas, prostate, blood, bladder, brain, bone, kidney, lung, liver, skin, ovarian, thyroid, gastrointestinal, head and neck, and neural, among others (Jemal et al. CA Cancer J. Clin. 2008, 58(2):71-96). Progress in cancer research has been slow since there are no drugs to cure cancer; hence, there is a persisting need to develop effective drugs and therapeutic-vaccine compounds that are more stable, more potent, with minimum or no toxicity, and that prolong the life of patients while providing significant improvement in their quality of life.
Pathological conditions of the eye include age-related macular degeneration, choroidal neovascularization, (AMD), proliferative diabetic retinopathy (PDR), diabetic macular edema (DME), among others. These diseases are the result of aberrant proliferation of new blood microvessels or neoangiogenesis (Hubschman et al. Clinical Ophthalmology 2009, 3 167-174). VEGF is a major factor in neovascular eye diseases and is the target by several anti-VEGF based therapies based on monoclonal antibodies. Unfortunately, such therapies induce considerably side effects, thus effective therapies are an unmet medical need.
Inflammation is a process by which the body's white blood cells and chemicals protect the body from infection and foreign substances such as bacteria and viruses. Many pro-angiogenic factors are mediators of inflammation (Campa et al. Mediators of Inflammation, Review Article. 2010, ID 546826, 1-14), and in some diseases, the body's immune system inappropriately triggers an inflammatory response when there are no foreign substances to fight off; in these autoimmune diseases, the body's normally protective immune system causes damage to its own tissues. Multiple sclerosis, type 1 diabetes mellitus, thyroiditis, rheumatoid arthritis and lupus, among others, are autoimmune diseases.
Receptors, found in the extra cellular matrix, are transmembrane proteins that bind ligands. Integrins are receptors for a variety of extra cellular matrix proteins mediating migration of endothelial cells, and regulating their growth, survival, and differentiation, but there are also present on tumor cells of various origins (Cox et al, Nat Rev Drug Discov. 2010, 9(10):804-20). Receptors involved in human diseases include VEGF receptors, G protein receptors, ERBB receptors, platelet derived growth factor receptor (PDGFR), CXR1, CXR2, CCR3, CCR5 receptors, and NOGO receptors, among others. Neurodegenerative diseases and mood disorders are example of diseases caused by the unbalanced neurotransmission of receptors and structural impairment of neuroplasticity. Chronic stress causes decrease of neurotrophin levels inducing depression. Antidepressants like lithium help increase expression of neurotrophins like BDNF and VEGF, thereby blocking, or reversing structural and functional pathologies via neurogenesis. Lithium also induces mood stabilization and neurogenesis due to the inhibition of glycogen synthase kinase-3beta (GSK-3beta), which allows the accumulation of beta-catenin. Increased levels of GSK-3beta and beta-catenin are associated with various neuropsychiatric and neurodegenerative diseases (Wada A. J Pharmacol Sci 2009, 110, 14-28). Inhibition of GSK-3 beta expression seems therefore beneficial to ameliorate and/or stabilize mood disorders and induce neurogenesis. The unbalanced presence of receptors also causes neurodegeneration. The Nogo receptor binds to the myelin-associated proteins Nogo-A, MAG, and OMgp, causing neurodegeneration. It can inhibit differentiation, migration, and neurite outgrowth of neurons, causing poor recovery of the adult central nervous system (CNS) from damage. Brain-derived neurotrophic factor stimulates the phosphorylation, suppressing Nogo-dependent inhibition of neurite outgrowth from neuroblastoma-derived neural cells; thus, it is important to control Nogo signaling to prevent neuronal damage.
Some proteins in the human body when suppressed exert a positive or beneficial effect. The target of rapamycin, mTOR, when inhibited suppresses the overexpression of HER2 oncoprotein, which is involved in cancer, or inhibits the process of aging by extending the lifespan of organisms (e.g., worms, fruit fly, yeast, and mice); mTOR, is therefore a suitable target to create potential anti-cancer and anti-aging compounds (Liu et al. Nature Reviews Drug Discovery 2009, 8:627-644). Many negative regulators of angiogenesis include thrombospondin-1, brain derived antiangiogenesis inhibitor, angiostatin, tropomyosin, among others. These proteins inhibit endothelial cell proliferation and tumor angiogenesis in vivo.
Diseases caused by pathogen agents include those acquired by blood borne pathogens (e.g., viruses such as HIV) through blood via infected people or animals, blood transfusions, or sexual contact; those caused by infectious agents like prions, which induce their own replication and derive from self; those caused by parasites (e.g., malaria, TB) acquired through bites by host organisms (e.g., insects, rodents), and those caused by pathogens acquired by contaminated food or water, (e.g., bacteria, fungi, yeast).
HIV/AIDS is a worldwide disease of large proportions for which there is no cure (Richman, et al. Science 2009, 323, 1304-1307). Prions contain a protein (PrP) 27-30, which aggregates forming amyloid plaques that accumulate selectively in the central nervous system cells causing neurodegenerative diseases such as Creuzfeldt-Jakob and Alzheimer's diseases, Down's syndrome, fatal familial insomnia, and recently, Parkinson's Disease. Prions are transmitted through contaminated plasma products, meat, and feeds or by person to person (Gu et al. JBC 2002, 277(3):2275-228). There are no drugs to treat prion infection.
Bacterial and parasitic infections are a worldwide health problem. Staphylococcus aureus (MRSA) is a highly infectious bacteria and the cause of worldwide nosocomial infections. (Kaufmann et al. Exper. Opin. Biol. Ther. 2008, 8(6):719-724). Tuberculosis, caused by the pathogenic bacteria Mycobacterium tuberculosis (Mtb), is presently the leading cause of death from infectious disease, infecting more than a third of the world's population (Ciulli et al. Chem Bio Chem 2008, 9, 2606-2611). It is acquired from small-infected mammals or by person to person. Salmonella typhimurium, other highly infectious and deadly bacteria, spreads by drinking contaminated water (Townes et al. Biochemical and Biophysical Research Communications 2009, 387: 500-503). Malaria, caused by the protozoan Plasmodium falciparum, is spread by mosquito bites infecting the red blood cells (VanBuskirk et al. PNAS, 2009, 106(31):13004-13009). Drugs approved to treat many of these diseases are single target drugs; most are non-specific, and do not cure the aimed disease; hence there is a persisting need to develop novel multi-targeted therapies
The diseases described above are the result of the abnormal balance of many proteins involved in different functions and physiological pathways in the body. The available single target drugs, provide a modest and transient clinical effect, but do not cure the aimed disease. Furthermore, clinical trials of drugs targeting many of these diseases have shown numerous times that targeting a single protein or an angiogenesis pathway or a single mechanism, or a disease condition, is unlikely to result in the best possible benefit for the patient. Therefore, it would be advantageous to create compounds comprising multiple different peptides each targeting specifically a particular pathologic protein. This approach may allow simultaneous interference at different levels in the angiogenic cascade or interference of different pathways leading to disease by targeting the functional domains of proteins involved in multiple diseases. For example, targeting simultaneously several proteins involved in abnormal angiogenesis would enable therapeutic applications for eye pathologies, cancer and other diseases. In view of the forgoing, it is appreciated that these multi-targeted compounds would be a significant advancement in the art.